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    <div class="refentry" id="glGetTransformFeedbackVarying">
      <div class="titlepage"/>
      <div class="refnamediv">
        <h2>Name</h2>
        <p>glGetTransformFeedbackVarying — retrieve information about varying variables selected for transform feedback</p>
      </div>
      <div class="refsynopsisdiv">
        <h2>C Specification</h2>
        <div class="funcsynopsis">
          <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
            <tr>
              <td>
                <code class="funcdef">void <strong class="fsfunc">glGetTransformFeedbackVarying</strong>(</code>
              </td>
              <td>GLuint <var class="pdparam">program</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>GLuint <var class="pdparam">index</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>GLsizei <var class="pdparam">bufSize</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>GLsizei * <var class="pdparam">length</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>GLsizei * <var class="pdparam">size</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>GLenum * <var class="pdparam">type</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>char * <var class="pdparam">name</var><code>)</code>;</td>
            </tr>
          </table>
          <div class="funcprototype-spacer"> </div>
        </div>
      </div>
      <div class="refsect1" id="parameters">
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>program</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    The name of the target program object.
                </p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>index</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    The index of the varying variable whose information to retrieve.
                </p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>bufSize</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    The maximum number of characters, including the null terminator, that may be written into <em class="parameter"><code>name</code></em>.
                </p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>length</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    The address of a variable which will receive the number of characters written into <em class="parameter"><code>name</code></em>,
                    excluding the null-terminator. If <em class="parameter"><code>length</code></em> is <code class="constant">NULL</code> no length is returned.
                </p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>size</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    The address of a variable that will receive the size of the varying.
                </p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>type</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    The address of a variable that will recieve the type of the varying.
                </p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>name</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    The address of a buffer into which will be written the name of the varying.
                </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1" id="description">
        <h2>Description</h2>
        <p>
            Information about the set of varying variables in a linked program that will be captured
            during transform feedback may be retrieved by calling <code class="function">glGetTransformFeedbackVarying</code>.
            <code class="function">glGetTransformFeedbackVarying</code> provides information about the varying
            variable selected by <em class="parameter"><code>index</code></em>. An <em class="parameter"><code>index</code></em> of 0 selects
            the first varying variable specified in the <em class="parameter"><code>varyings</code></em> array passed
            to <a class="citerefentry" href="glTransformFeedbackVaryings.xhtml"><span class="citerefentry"><span class="refentrytitle">glTransformFeedbackVaryings</span></span></a>, and
            an <em class="parameter"><code>index</code></em> of <code class="constant">GL_TRANSFORM_FEEDBACK_VARYINGS-1</code> selects
            the last such variable.
        </p>
        <p>
            The name of the selected varying is returned as a null-terminated string in
            <em class="parameter"><code>name</code></em>. The actual number of characters written into <em class="parameter"><code>name</code></em>,
            excluding the null terminator, is returned in <em class="parameter"><code>length</code></em>. If <em class="parameter"><code>length</code></em>
            is NULL, no length is returned. The maximum number of characters that may be written into <em class="parameter"><code>name</code></em>,
            including the null terminator, is specified by <em class="parameter"><code>bufSize</code></em>.
        </p>
        <p>
            The length of the longest varying name in program is given by <code class="constant">GL_TRANSFORM_FEEDBACK_VARYING_MAX_LENGTH</code>,
            which can be queried with <a class="citerefentry" href="glGetProgramiv.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetProgramiv</span></span></a>.
        </p>
        <p>
            For the selected varying variable, its type is returned into <em class="parameter"><code>type</code></em>. The size of
            the varying is returned into <em class="parameter"><code>size</code></em>. The value in <em class="parameter"><code>size</code></em> is
            in units of the type returned in <em class="parameter"><code>type</code></em>. The type returned can be any of the
            scalar, vector, or matrix attribute types returned by <a class="citerefentry" href="glGetActiveAttrib.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetActiveAttrib</span></span></a>.
            If an error occurred, the return parameters <em class="parameter"><code>length</code></em>, <em class="parameter"><code>size</code></em>,
            <em class="parameter"><code>type</code></em> and <em class="parameter"><code>name</code></em> will be unmodified. This command will return as much
            information about the varying variables as possible. If no information is available, <em class="parameter"><code>length</code></em>
            will be set to zero and <em class="parameter"><code>name</code></em> will be an empty string. This situation could
            arise if <code class="function">glGetTransformFeedbackVarying</code> is called after a failed link.
        </p>
      </div>
      <div class="refsect1" id="errors">
        <h2>Errors</h2>
        <p>
            <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>program</code></em> is not
            the name of a program object.
        </p>
        <p>
            <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>index</code></em> is greater or equal to
            the value of <code class="constant">GL_TRANSFORM_FEEDBACK_VARYINGS</code>.
        </p>
        <p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated <em class="parameter"><code>program</code></em> has not been linked.
        </p>
      </div>
      <div class="refsect1" id="associatedgets">
        <h2>Associated Gets</h2>
        <p>
            <a class="citerefentry" href="glGetProgramiv.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetProgramiv</span></span></a> with argument <code class="constant">GL_TRANSFORM_FEEDBACK_VARYING_MAX_LENGTH</code>
                        or <code class="constant">GL_TRANSFORM_FEEDBACK_VARYINGS</code>.
        </p>
      </div>
      <div class="refsect1" id="versions">
        <h2>API Version Support</h2>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
            <colgroup>
              <col style="text-align: left; "/>
              <col style="text-align: center; " class="firstvers"/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; " class="lastvers"/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; ">
                 
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; " colspan="4">
                <span class="bold"><strong>OpenGL ES API Version</strong></span>
            </th>
              </tr>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>Function Name</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>2.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.1</strong></span>
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.2</strong></span>
            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">glGetTransformFeedbackVarying</td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; ">✔</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="seealso">
        <h2>See Also</h2>
        <p>
            <a class="citerefentry" href="glBeginTransformFeedback.xhtml"><span class="citerefentry"><span class="refentrytitle">glBeginTransformFeedback</span></span></a>,
            <a class="citerefentry" href="glEndTransformFeedback.xhtml"><span class="citerefentry"><span class="refentrytitle">glEndTransformFeedback</span></span></a>,
            <a class="citerefentry" href="glTransformFeedbackVaryings.xhtml"><span class="citerefentry"><span class="refentrytitle">glTransformFeedbackVaryings</span></span></a>,
            <a class="citerefentry" href="glGetProgramiv.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetProgramiv</span></span></a>
        </p>
      </div>
      <div class="refsect1" id="Copyright">
        <h2>Copyright</h2>
        <p>
            Copyright <span class="trademark"/>© 2010-2015 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="link" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p>
      </div>
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